Fear can be acquired vicariously through social observation of others suffering from aversive stimuli.We have developed a robust assay in which a mouse can be conditioned for fear associated with a context without direct experience of aversive stimulus (unconditioned stimulus) but by observing other mice (demonstrator) receiving repetitive foot shocks.The degree of the conditioning was increased when the demonstrator mouse was related to the observer mouse, such as siblings or mating partners.These findings suggest that this observational fear learning is mediated by empathy.Using local inactivation techniques, we showed that anterior cingulate cortex (ACC) and parafascicular or mediodorsal thalamic nuclei, which comprise the medial pain system for pain affection, are critically involved in this observational fear learning, whereas inactivation of sensory thalamic nuclei had no effect.During the observational fear learning, the ACC neuronal activities were increased and synchronized with those of the lateral amygdala at the theta rhythm frequency.Using the local gene deletion techniques, we also showed that Cavl.2 Ca2+ channels in the ACC is required for observational fear learning, suggesting the involvement of Cav 1.2 channels of the ACC in this empathy fear.Currently, we are trying to define further the circuits underlying the cortical mechanism for this social learning behavior.